1. Field of the Invention
The present invention relates to a technique of measuring average postprandial blood glucose.
2. Related Art
Postprandial blood glucose measurement has lately come to be spotlighted as an important procedure in blood glucose control. As an index indicating the severity of diabetes the level of average postprandial blood glucose is popularly adopted, and measured data thereof is utilized to evaluate the sugar metabolism performance of a patient.
The postprandial blood glucose (instantaneous blood glucose) incessantly fluctuates with the lapse of time after meal, and hence the blood glucose measurement has conventionally been executed over a plurality of times at short intervals after meal, in order to calculate the average postprandial blood glucose. The calculation of the average postprandial blood glucose is obtained through drawing a curve representing the blood glucose fluctuation based on the instantaneous blood glucose, which is fluctuating time after time, calculating the Area of a region Under the Curve but upper than a predetermined renal glucose excretion threshold (hereinafter, AUC), and then calculating the time-based average of the AUC.
For individual patients, however, it is a burden to measure the instantaneous blood glucose over a plurality of times after every meal, and therefore a technique that allows diabetic patients and those who have high blood glucose levels to daily and simply check the average postprandial blood glucose has been eagerly sought for.
The solution conventionally attempted includes estimating the instantaneous blood glucose based on urinary glucose. To cite a few examples, JP-A No. 2003-270241 discloses a technique of estimating the instantaneous blood glucose of a subject at the time of the measurement, by storing in advance the long-term fluctuation pattern of the urinary glucose of the subject. Also, JP-A No. 2004-286452 teaches a method of estimating the instantaneous blood glucose based on the urinary glucose of the subject measured upon collecting the urine, by statistically analyzing in advance the relationship between the urinary glucose and the blood glucose with respect to each individual subject.    [Patent document 1] JP-A No. 2003-270241    [Patent document 2] JP-A No. 2004-286452    [Non-patent document 1] The Japanese Journal of Clinical Medicine, p. 524-525, Vol. 60, Special Edition No. 8, 2002 published by Nippon Rinsho Co., Ltd.
The measurement of the postprandial urinary glucose is easy and hence offers the advantage that the patient is exempted from the burden, compared with the direct measurement of the blood sugar concentration executed through collecting the blood. The urinary glucose is, however, prone to largely fluctuate in case that the urine is condensed or diluted by water intake or excretion by the patient (except urination), such as drinking water or perspiration, and hence it has been widely believed that it is technically difficult to accurately estimate the instantaneous blood glucose based on the urinary glucose (Ref. the non-patent document 1). In other words, the urinary glucose is an integral parameter determined by the amount of urine stored in the urinary bladder after the previous urination and the amount of urinary glucose contained therein, and therefore such parameter is considered to be inappropriate for estimating the instantaneous blood glucose, which fluctuates time after time.
The patent document 1 does not provide a specific method of estimating the instantaneous blood glucose based on the urinary glucose. Moreover, the procedure according to this literature requires accumulating the correlation between the urinary glucose and the instantaneous blood glucose of the subject over a long period of time and establishing the correlation as data in advance. This point constitutes a major drawback that the procedure is inapplicable to general patients whose long-term correlation data acquired as above is unavailable.
This is also the case with the patent document 2, which requires acquiring the statistical data in advance, with respect to each patient.
Meanwhile, since the conventional measurement of the average postprandial blood glucose requires establishing a time-serial fluctuation pattern of the instantaneous blood glucose fluctuating time after time, the calculation thereof based on the urinary glucose is not involved.
In the case of the method according to the patent document 2 for example, it is an excessive burden for the patient to collect a predetermined amount of urine at short intervals, such as every 15 minutes or every 30 minutes, after each meal. Besides, since a sufficient amount of urine is not always collectable, it is practically impossible to draw an accurate blood glucose curve to thereby calculate the AUC, despite the trouble of repeatedly measuring the urinary glucose and converting the value into the instantaneous blood glucose.
Consequently, it is impossible to acquire the average postprandial blood glucose based on the measured level of the urinary glucose, as long as depending on the fluctuation pattern of the instantaneous blood glucose as in the conventional methods, to calculate the average postprandial blood glucose. Thus, actually it has been the only way for acquiring the average postprandial blood glucose, to repeatedly measure the blood sugar concentration at short intervals.
The present invention has been accomplished in view of the foregoing problem, and provides a practical measuring device that allows a patient to simply measure the average postprandial blood glucose based on the urinary glucose, and a method of measuring the same.